It is well established that both acute and chronic sun exposure has general detrimental effects to the skin over time. Intervention with the use of sunscreens and sunblocks at a young age is advocated by dermatologists around the world. However compliance is minimal. Avoidance of sun exposure early in life is thought to be particularly important because the carcinogenic effects of the sun are cumulative and are manifested years after the exposure. For children, compliance is dependent primarily on the diligence of the parents. During the teenage years responsibility shifts to the individual, yet teenagers are notoriously noncompliant with the use of sunscreens. In fact the “sun exposed appearance” is regarded as desirable among teenagers generally. Sunscreen use for outdoor activities by adolescents and young adults is highly important for healthy skin, i.e., to minimize the risk of developing skin cancers and to reduce the premature signs of skin aging over time. Therefore, the public health need is great to improve and to facilitate the regular use of sunscreens among adolescents and young adults. It is particularly important to protect the facial area which receives intense and repeated sun exposure.
Recent studies published by the American Academy of Dermatology highlight the lack of compliance of young adults and teenagers in the use of sunscreens. In a study entitled “New American Academy of Dermatology Survey Finds People Aware of the Dangers of the Sun, But Sun Protection Not Necessarily Practiced,” Am. Acad. Dermatol. (Apr. 29, 2003), it was reported that, although 79% of surveyed parents and grandparents apply sunscreen to children when they play outdoors, this number drops to only 34% for independent young people under the age of 25. In another study entitled, “New Study Finds High School Students Get Enough UV Exposure on an Average Day to Cause Sunburn”, Am. Acad. Dermatol. (Apr. 24, 2002), it was reported that, when high school students between the ages of 12 and 17 were provided with Ultraviolet B dosimeters to wear on their wrists, UVB exposure that occurred during regular daily activities was sufficient to cause sunburn in some students. Moreover, even though UVB exposure was less on cloudy days, the amount of UVB exposure on these days was higher than expected and 80% of the sun's UV rays pass through the clouds. The study also estimated that almost 80% of a person's lifetime sun exposure occurs before the age of 18 Therefore, reducing the exposure of teenagers to harmful rays of the sun is extremely important. In another study entitled “Skin Cancer Awareness and Sun Protection Behaviors in College Students”, J. Acad. Dermatol., Abstract P1321, page P107 (March 2005), it was reported that the majority of college students do not use sunscreen on a regular basis. In fact, fully 81% of college students surveyed reported that they never, rarely, or only sometimes use sunscreen.
In a recent article, Kullavanijaya, P, and Lim, H W, J. Am. Acad. Dermatol., 52:937-958 (June 2005), incorporated herein by reference, review the various types of ultraviolet radiation, the harms that these rays can cause upon exposure to skin, and various types of sun protective agents that are applied to protect the skin. As disclosed by Kullavanijaya and Lim, most presently available sunscreen agents are effective primarily in blocking UVB rays and are photolabile, that is they are degraded upon exposure to ultraviolet radiation. Many of the available sunscreens also induce adverse effects such as irritation, allergic contact reactions, photoallergy, and phototoxic effects.
Newer sunscreen agents such as benzene 1,4-di(3-methylidene-10-camphosulfonic acid (MEXORYL SX®, L'Oreal, Clichy, France) (described in U.S. Pat. No. 4,585,597, incorporated herein by reference), drometriazole trisiloxane (MEXORYL XL®, L'Oreal, Clichy, France) (described in U.S. Pat. No. 4,585,597), methylene-bis-benzotriazoyl tetramethylbutylphenol (bisoctrizole, TINOSORB M®, Ciba Specialty Chemicals, Basel, Switzerland) (described in U.S. Pat. Nos. 5,869,030; 5,980,872; and 6,521,217, each of which is incorporated herein by reference), and bis-ethylhexyloxyphenol methoxyphenol triazine (anisotriazine, TINOSORB S®, Ciba Specialty Chemicals) (described in U.S. Pat. Nos. 5,869,030; 5,980,872; and 6,521,217), as well as the inorganic sunscreen agents titanium oxide (TiO2) and zinc oxide (ZnO) are reported by Kullavanijaya and Lim to not share these disadvantages. These agents are broad spectrum UV absorbers, are photostable, and have not been found to cause the adverse effects associated with other sunscreen agents.
Acne vulgaris, often referred to as “acne”, is a condition that is distinct from and is not related to acne rosacea. Acne vulgaris is a disorder of the pilosebaceous follicle. Common features of acne vulgaris include increased sebum production, follicular keratinization, colonization by Propionibacierium acnes, and localized inflammation.
Treatment for acne vulgaris is typically with one or more of a retinoid, such as tretinoin or isotretinoin, an antibiotic, such as clindamycin or erythromycin, or other medication such as azelaic acid, a sulfonamide, and antibacterials such as benzoyl peroxide. Retinoid compounds increase the sensitivity of skin to the sun and are often inactivated by ultraviolet light. Therefore, retinoid products are recommended to be used at night or together with a sunscreen. Sulfonamides likewise increase the sensitivity of skin to the sun and, therefore, may be combined with a sunscreen. Benzoyl peroxide is highly reactive and degrades upon exposure to the sun. Therefore, benzoyl peroxide may be combined with a physical sunscreen to inhibit this sun-induced degradation. Such problems have not been associated with the use of antibiotics, such as those of the lincomycin family, or with azelaic acid or salicylic acid.
Acne rosacea, often referred to simply as rosacea, is a separate distinct dermatological disorder, which is a chronic inflammatory skin disorder characterized by enhanced epidermal proliferation leading to erythema, typically with flushing, scaling, and thickening of the skin. Rosacea is often exacerbated by exposure to the sun. Therefore, treatment of rosacea often includes the use of sunscreens. In contrast to rosacea, acne vulgaris primarily affects young people, during the teenage years and sunscreens have no known beneficial role in treating acne vulgaris. In fact many sunscreens have been reported to be comedogenic, that is they have the potential to induce comedones which are the primary lesions of acne vulgaris.
The present invention is directed to methods of treating and preventing or inhibiting recurrences of acne vulgaris and addresses the significant need for increasing the compliance in the application of topical sunscreens in individuals suffering from or at risk of developing acne vulgaris, primarily teenagers and other adolescents and young adults. In this way, chronic effects of overexposure to harmful rays of the sun, such as skin cancers, can be greatly reduced.